Manufacture of coated wire



Dec. 19, 1967 5. M. JOST 3,359,096

MANUFACTURE OF COATED WIRE Filed May 11, 1966 FIG.I.

United States Patent Ofiice 3,359,996 Patented Dec. 19, 1967 3,359,096 MANUFACTURE OF COATED WIRE Ernest M. Jost, Plainville, Mass., assignor to Texas Instruments Incorporated, Dallas, Tex., a corporation of Delaware Filed May 11, 1966, Ser. No. 549,327 4 Claims. (Cl. 75201) ABSTRACT OF THE DISCLOSURE Coated wire is manufactured by applying to a moving core wire a coating of a wet viscous slurry comprising a binding compound, a liquid and particles of metal in finely divided or powder form. Part of the adhering slurry is stripped from the wire as the coating is removed from a slurry pool, thereby determining and making even the thickness of the viscous coating around the wire. The coating 'is then dried by heating and sintered to bond the coating particles to one another and to the core wire. The dried and sintered coated wire is then subjected to circumscribing pressure to reduce the thickness of coating. Coating, stripping, drying, sintering and reduction are performed in a single pass of the wire through the process.

Among the several objects of the invention may be noted'the provision of improved method and apparatus for manufacturing coated wire using metal particles to coat it; the provision of method and apparatus for firmly bonding a dense metal layer to a core wire from a slurry containing particles of the coating metal; and the provision of a coated Wire manufactured according to the invention. Other objects and features will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the constructions, products and methods hereinafter described, the scope of the invention being indicated in the following claims. i

In the accompanying drawings, in which one of various possible embodiments of the invention is illustrated,

FIG. 1 is a diagrammatic view illustrating manufacture of coated wire in accordance with the invention;

FIGS. 2, 3 and 4 are cross sections taken on lines 22, 3-3 and 44 of FIG. 1 illustrating coating of a core wire according to the invention; and

FIG. 5 is a cross section taken along line 55 of FIG. 1, showing a coated wire manufactured according to the invention.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

In the following description, the term metals includes alloys. The term slurry means a liquid medium of substantial viscosity containing metal particles suspended in a binder. The term binder means, for example, longchain high-molecular-weight organic compounds or the like characterized in that their constituents when comminuted are stringy and when mixed with a liquid such as water swell and act according to the invention to hold or bind the metal particles in suspension and to produce adequate viscosity in the slurry and cause it to adhere to metal surfaces contacted by it. Examples but without limitation, of suitable binders are polyethylene oxide, methyl cellulose, cellulose triacetate, polyvinyl alcohol et cetera. The drawings are illustrative and not to scale because of the small dimensions involved.

Briefly, the process for manufacturing coated wire according to the present invention comprises coating a core wire with a slurry containing a metal powder suspended in a binder, drying the slurry on the wire, then sintering metal particles to each other and to the core Wire, and subsequently squeezing the coated wire.

The slurry includes a mixture of a binder such as mentioned above, a carrier such as water and a powder containing particles of the metal which is to be coated on the core wire. The average size of the particles in the powder is preferably very small -(e.g., less than 50 microns) since the core wire is usually small in diameter. The particles are suspended and preferably evenly distributed throughout the binder. The slurry may contain any suitable metal particles, such as nickel, copper, aluminum, iron, tin, et cetera. The quantity of the binder used controls the viscosity of the slurry. The slurry viscosity is controlled so that when it is applied to a core wire it will cling to the wire. In some (but not all) cases a conventional wetting agent such as sodium tetradecyl sulfate or potassium cocoate can be used to advantage in the slurry. The total solid content is preferably high and desirably exceeds 50% by weight of the total weight of the slurry. By way of example, the slurry may comprise about 650 grams of Inco type 255 carbonyl-nickel powder in approximately 650 cubic centimeters of five percent polyethylene oxide aqueous solution.

After the slurry has been thoroughly mixed, it is poured into a tank or container as shown at 1 in FIG. 1. The slurry is designated 3 in the drawings and may be agitated or circulated by a stirrer illustrated diagrammatically at 5 to maintain the metal particles and liquid solutions of the slurry in a thoroughly mixed and homogenous state.

A core Wire 7 is unwound from a supply reel 9 of the wire and it is subsequently rewound after being coated on a take-up reel 11 at the other end of the apparatus. The wire may be composed of copper, iron or other suitable materials. Wire 7 is trained around a series of guide rolls, each of which is designated 13, so that it travels through the pool of slurry in the container. As the wire moves through the container a coating 18 (FIG. 3) of the slurry 3 is deposited on the wire and held on the wire by the binding compound.

The wire 7 leaves the container 1 through a hole 17 in a stripping die generally designated 15. The size of the hole determines the thickness of the slurry coating retained on the wire as it leaves the container.

The coated core wire is then passed through a retort 19 where the wire and coating are heated. This heating can be achieved in any suitable manner. As shown in the drawings, the wire 7 is resistance-heated from a source of DC. power 21, one contact of the power source being connected by a conductor 23 to the slurry bath 3 and the other contact of the power source being connected by a conductor 25 to the upper roll 27 of draw rolls 27 and 29 which receive the wire after it leaves retort 19. Current is conducted in the slurry by the metal particles and to some extent by the slurry liquid. Alternatively, the power source 21 may be connected directly to the wire prior to the time it enters bath 3 and subsequent to the time it leaves retort 19. The retort preferably contains a reducing atmosphere such as hydrogen. As the wire is heated in the retort, the binder is burned off and the water or other liquids used in making the slurry are vaporized. This leaves a dry coating on the core Wire comprising metal particles from the slurry 3. Heating of the core wire continues until metal particles on the core wire are sintered to each other and to the core wire. Sintering can be done as a separate step in a sintering furnace, if desired. The sintering temperature will vary, depending on the metal used, and may be about 1800 F. for nickel. When the wire and coating leave the retort 19 they are firmly bonded to each other. The sintered coating is designated 26 in FIG. 4.

Next the wire and coating are passed between and squeezed by the rolls 27 and 29 of a conventional rolling mill to reduce the size of the coated wire to the desired diameter or shape. Both the coating and the core wire may be reduced, or only the coating. Reduction is preferably accomplished while the wire is hot. Reduction may also be achieved by swaging or drawing.

The resulting coated wire is illustrated in FIG. 5 and comprises the core wire 7 and a coating 31 which is substantially uniform in thickness and is firmly bonded to the core wire throughout the circumference of the core Wire. Coating 31 consists essentially of a dense metal layer formed from sintered and squeezed particles of the metal powder used in making the slurry 3. After the coated Wire leaves the forming rolls, it is wound on the take-up reel 11.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above methods, constructions and products without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is: 1. The continuous single-pass method of manufacturing coated wire comprising,

coating a core-forming wire with a wet viscous coating comprising a binding compound, a liquid and particles of metal in powder form, by moving the core wire first through a pool of slurry containing the coating materials, stripping any excess coating from th wire immediately after the coating has been applied to the wire and while the coating is still wet and viscous thereby to regulate the thickness of the coating around the Wire, heating the coated wire in a reducing atmosphere to dry the coating and to drive 01f substantially all of the binding compound and other liquids from the coating to leave a dry coating on the wire comprising particles of metal from the slurry, further heating the coating to sinter metal particles of the dry coating to each other and to the core wire 4 thereby firmly bonding the dry coating and core wire to each other, and

under pressure reducing the thickness of the dried and sintered coating to a substantially uniform thickness around the wire, thereby providing a firmly bonded homogenous dense coating of metal around the core wire throughout its circumference.

2. The method according to claim 1 wherein,

heating of the wire is accomplished by passing the wet coated wire from the pool through a retort and passing electric current through the wire between a point ahead of its outlet from the pool and a point beyond the retort, and

reduction is effected while the dry-coated wire is hot by compressive draw rolls which move the wire through said single pass.

3. The method according to claim 2 wherein the total solid content of the slurry exceeds percent by total weight of the slurry and the average size of the metal particles in the slurry is less than 50 microns.

4. The method according to claim 1 wherein the binding compound comprises a polyethylene oxide aqueous solution, the total solid content of the slurry exceeds 50" percent by total weight of the slurry, and the average size of the metal particles in the slurry is less than 50 microns.

References Cited UNITED STATES PATENTS 2,819,962 1/1958 Salauze --208 3,002,930 10/1961 Robinson 75212X 3,050,386 8/1962 Von Dohren 75-222X 3,066,407 12/1962 Toensing.

3,086,860 4/1963 Montaud 75-222 3,109,745 11/1963 Begany 117-128X 3,214,270 10/1965 Valyi 75-201 3,284,892 11/1966 Wade 29--528X FOREIGN PATENTS 471,778 2/1951 Canada.

L. DEWAYNE RUTLEDGE, Primary Examiner.

BENJAMIN R. PADGETT, Examiner.

A. J. STEINER, Assistant Examiner. 

1. THE CONTINUOUS SINGLE-PASS METHOD OF MANUFACTURING COATED WIRE COMPRISING, COATING A CORE-FORMING WIRE WITH A WET VISCOUS COATING COMPRISING A BINDING COMPOUND, A LIQUID AND PARTICLES OF METAL IN POWDER FORM, BY MOVING THE CORE WIRE FIRST THROUGHA POOL OF SLURRY CONTAINING THE COATING MATERIALS, STRIPPING ANY EXCESS COATING FROM THE WIRE IMMEDIATELY AFTER THE COATING HAS BEEN APPLIED TO THE WIRE AND WHILE THE COATING IS STILL WET AND VISCOUS THEREBY TO REGULATE THE THICKNESS OF THE COATING AROUND THE WIRE, HEATING THE COATED WIRE IN A REDUCING ATMOSPHERE TO DRY THE COATING AND TO DRIVE OFF SUBSTANTIALLY ALL OF THE BINDING COMPOUND AND OTHER LIQUIDS FROM THE COATING TO LEAVE A DRY COATING ON THE WIRE COMPRISING PARTICLES OF METAL FROM THE SLURRY, FURTHER HEATING THE COATING TO SINTER METAL PARTICLES OF THE DRY COATING TO EACH OTHER AND TO THE CORE WIRE THEREBY FIRMLY BONDING THE DRY COATING AND CORE WIRE TO EACH OTHER, AND UNDER PRESSURE REDUCING THE THICKNESS OF THE DRIED AND SINTERED COATING TO A SUBSTANTIALLY UNIFORM THICKNESS AROUNG THE WIRE, THEREBY PROVIDING A FIRMLY BONDED HOMOGENOUS DENSE COATING OF METAL AROUND THE CORE WIRE THROUGHOUT ITS CIRCUMFERENCE. 